| Kaatedocus | |
|---|---|
 | |
| Mounted skeleton cast,Museum of Natural Sciences of Belgium inBrussels. | |
Scientific classification | |
| Kingdom: | Animalia |
| Phylum: | Chordata |
| Class: | Reptilia |
| Clade: | Dinosauria |
| Clade: | Saurischia |
| Clade: | †Sauropodomorpha |
| Clade: | †Sauropoda |
| Superfamily: | †Diplodocoidea |
| Clade: | †Flagellicaudata |
| Genus: | †Kaatedocus Tschopp &Mateus,2012 |
| Type species | |
| †Kaatedocus siberi Tschopp & Mateus, 2012 | |
Kaatedocus is agenus offlagellicaudatansauropod known from the middleLate Jurassic (Kimmeridgian stage) of northernWyoming, United States. It is known from well-preservedskull andcervical vertebrae which were collected in the lower part of theMorrison Formation. Thetype and only species isKaatedocus siberi, described in2012 byEmanuel Tschopp andOctávio Mateus.[1]
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In 1934, a team of theAmerican Museum of Natural History (AMNH) headed byBarnum Brown, financed by theSinclair Oil Corporation, uncovered about three thousand sauropod bones on the land of rancher Barker Howe nearShell, inBig Horn County. Plans for further excavations in 1935 had to be cancelled after Howe, convinced by the large publicity surrounding the find that the remains were very valuable, demanded higher payment. The bones would not be described and most of them were lost in a fire at the AMNH during the 1940s; others were thrown away in the 1960s after having rotted because of being stowed in a chicken run at Shell. Only about 10% of the fossils survived, among them a skull. They were generally interpreted as belonging toBarosaurus. In 2015, based on specimen-level phylogenetic analysis, one of these specimens (AMNH FARB 7530) was reinterpreted to belong toKaatedocus.[2]
In 1989 the site was reopened byHans-Jakob Siber, the founder of the SwissAathal Dinosaur Museum. His team immediately adjacent to the old Howe Quarry discovered another 450 bones that became part of the collection of the Swiss museum.
The finds included an exceptionally complete neck, specimen SMA 004 In Switzerland, this became the subject of several lines of scientific investigation. In 2005 Daniela Schwarz studied the pneumatisation of the vertebrae bytomography scanning them withneutrons andX-rays.[3] In 2010Andreas Christian used the well-preserved vertebrae to support his hypothesis that sauropod necks were held in a rather upright position,[4] which was confirmed byArmin Schmitt studying thevestibular system ofKaatedocus. In 2012 Tschopp used a scan to create a replica of the neck by means of a3D-printer.[5]
During the intense study of the fossils it became clear that they did not representBarosaurus but a species new to science. In 2012 this was namedKaatedocus siberi, by the Swiss palaeontologist Emanuel Tschopp, who as a boy had visited the excavations, and his Portuguese colleague Octávio Mateus. The generic name, which means "small beam", combines a reference to the related formDiplodocus with aCrow Indiandiminutivesuffix~kaate. Thespecific name honours Siber.[1]
An additional specimen consisting of a braincase from the Aathal Dinosaur Museum collection (SMA D16-3) was referred toKaatedocus in 2013,[6] and its referral was corroborated in 2015 based on an exhaustive phylogenetic analysis.[2]
Kaatedocus was relatively small compared to most diplodocids. The type individual was estimated to have been approximately 14 metres (46 ft) long. The combined length of the skull and neck is approximately 3.8 metres (12 ft). The neck was composed of at least 14 vertebrae, comparable to the typical number in diplodocids.[1]
Tschopp, Mateus, and Benson (2015) foundKaatedocus to be an advanced member of the Diplodocinae, closely related toBarosaurus, as shown below.[2]
On the other hand, Whitlock and Wilson (2020) findKaatedocus to be the most basaldicraeosaurid, finding such a position more likely than being a diplodocid. The position ofKaatedocus is supported by many cranial features, which are only found within Diplodocoidea. The cladogram of the analysis is shown below:[7]
To support their analysis, Whitlock and Wilson evaluated the characters thatKaatedocus supposedly shared with Diplodocidae: "antorbital fenestra with concave dorsal margin; a 'hooked' prefrontal; box-like basal tubera; and the elongate coel on posterior cervical neural spines." They found the first character to be a more general character diagnostic ofFlagellicaudata, because it is currently unknown if dicraeosaurids possessed this feature. They believed that the second character, the hooked prefrontal, was incorrectly interpreted, and that the prefrontal is actually linear, similar toDicraeosaurus. The presence of a box-like basal tubera was excluded as a character from their analysis because the original intent of the character was to distinguishDiplodocus andApatosaurus, but in its current form, all other taxa exhibit intermediate morphologies. Lastly, the fourth character was also dismissed because it was unclear in its current definition and varied along the spinal column of all diplodocid taxa. Additionally, they independently test their results by conducting a supplemental analysis utilizing a modified dataset of Mannionet al. (2019)[8] which also recoveredKaatedocus within Dicraeosauridae.[7]
